Pakistan's military has strenuously rejected allegations by a British academic that al-Qaida is targeting the country's nuclear facilities in an attempt to obtain weapons for use against the west.

In an article for a US military journal, Professor Shaun Gregory, of the University of Bradford, said al-Qaida and the Taliban had targeted the country's nuclear infrastructure three times in the last two years.

Gregory cited suicide attacks on a "nuclear missile site", a "nuclear airbase" and a munitions complex at Wah, close to Islamabad, described as "one of Pakistan's main nuclear weapons assembly sites".

"The risk of the transfer of nuclear weapons, weapons components or nuclear expertise to terrorists in Pakistan is genuine," he wrote.

A military spokesman, Major General Athar Abbas, said Gregory's claims were "factually incorrect" and part of a western propaganda campaign to "malign Pakistan and its nuclear facilities".

The bases at Wah, Sargodha and Kamra were used to manufacture conventional weapons, ammunition and fighters jet, he said. "There are military facilities, not nuclear installations."

The suicide attacks were widely reported when they occurred and generally were not linked to Pakistan's secretive nuclear programme, which has an estimated 60 to 100 warheads.

Gregory cited a US website, the Long War Journal, as the source for his claims, the most contentious of which surrounds the Wah complex. When it was bombed in August 2008, a Taliban spokesman claimed responsibility, saying it was retaliation for army-inflicted civilian deaths in the tribal belt.

Talat Masood, a retired general and political analyst who ran the factory for eight years in the 1980s, said the nuclear link was "absolute nonsense".

The only known overt Taliban strike against Pakistan's nuclear infrastructure occurred last month, when a motorcycle-riding suicide bomber hit a bus carrying employees of Kahuta Research Laboratories, a major uranium enrichment facility, as it passed through Rawalpindi. Up to six people were killed.

Pakistan's nuclear programme is a source of both immense national pride and sensitivity. According to a popular conspiracy theory, the US is fomenting the Taliban insurgency to create an excuse for American troops to disarm the warheads.

In recent years as the country plunged into turmoil, the Pakistani military has reached out to stress the security of its atomic assets. The Strategic Plans Division, which oversees nuclear operations, regularly briefs visiting diplomats and journalists about safeguards it describes as world-class.

One element is the personnel reliability programme, modelled on a similar US initiative, which regularly screens nuclear workers for "Islamist sympathies, personality problems, drug use, inappropriate external affiliations, and sexual deviancy," according to Gregory. The army has jealously resisted US efforts to assert control over its security measures.

The clashes occurred in Jandola, a town on the edge of South Wazisitan, between forces loyal to Mehsud and the pro-government tribal leader Turkistan Bhittani. Mehsud is thought to have died in a US drone strike on 5 August. Taliban commanders insist he survived but have produced no proof to back their claim.